At the present time, pleasure craft, sailboats, and similar watercraft use a variety of self-steering systems and autopilots. These self-steering systems differ according to two different operating principles:
First, there are self-steering systems in the form of wind vanes that have a purely mechanical mode of operation, whereby the direction of movement of the watercraft is manipulated by the mechanical transmission of force between a wind vane and a pendulum-type rudder that works in the opposite direction. Self-steering systems of this kind are used exclusively on sailboats, and are suitable only for keeping the watercraft or the sailboat on the correct course relative to the wind. As soon as the direction of the wind changes, the sailboat leaves its compass course and follows the rotation of the wind. Self-steering systems of this kind operate without using any electrical current. They can only be manipulated mechanically.
There are, secondly, also self-steering systems that operate electronically. These are the so-called flux gate compass systems. These self-steering systems sample the Earth's magnetic field by means of built-in field coils and determine the angle between the longitudinal axis of the vessel and the lines of force that run between the Earth's poles. Such electronic self-steering systems always steer the watercraft on the compass course that is set at the time the self-steering system is switched on. Such electronic self-steering systems can also be combined with wind vanes. The steering movements that are required to keep on course, and which have to adjust the helm, are transmitted by means of a control device in the form of adjusting or servomotors.
The autopilots described above can keep a watercraft on course with sufficient safety and can provide the crew, which is usually small, with adequate relief from monotonous spells of work at the helm. Providing they are functioning properly, the steering accuracy offered by autopilots is much greater than can be achieved by a human helmsman or operator.
The great disadvantage of autopilots of this kind is that the watercraft will continue its course without change if the sole skipper or operator who is at the helm goes overboard. This danger exists not only for solo sailors, but also for crews such as families. There have been cases of the total loss of both crew and boat when the skipper or operator has gone overboard and the crew, frequently wife and children, were unable to turn the vessel, pick up the skipper or operator, and continue their voyage.